The ratio of uphill pace to downhill pace in a foot race up and down a single mountain is used as a measure of a competitor's descending skills-those qualities which are needed for fast descent but not for ascent. For the set of competitors in each of 44 races on seven courses of differing gradients and terrain roughnesses, we calculate the variance of this pace ratio and do linear regressions of pace ratio on finish time and on competitors' age. The variances tend to be greater for races on steeper and rougher terrain, indicating a greater influence of descending skills on actual descent speeds in these races. The regression analysis shows a clear negative correlation with finish time, indicating that faster finishers tend to be those with better descending skills, but there is little evidence of correlation with age. Significant differences between the sexes are only found in races on the most difficult terrain, where men display better descending skills than women.